Spectrally interleaved topologies using geometric phase metasurfaces.

Metasurfaces facilitate the interleaving of multiple topologies in an ultra-thin photonic system. Here, we report on the spectral interleaving of topological states of light using a geometric phase metasurface. We realize that a dielectric spectrally interleaved metasurface generates multiple interleaved vortex beams at different wavelengths. By harnessing the space-variant polarization manipulations that are enabled by the geometric phase mechanism, a vectorial vortex array is implemented. The presented interleaved topologies concept can greatly enhance the functionality of advanced microscopy and communication systems.

Quantum entanglement of the spin and orbital angular momentum of photons using metamaterials.

Metamaterials constructed from deep subwavelength building blocks have been used to demonstrate phenomena ranging from negative refractive index and ε-near-zero to cloaking, emulations of general relativity, and superresolution imaging. More recently, metamaterials have been suggested as a new platform for quantum optics. We present the use of a dielectric metasurface to generate entanglement between the spin and orbital angular momentum of photons. We demonstrate the generation of the four Bell states on a single photon by using the geometric phase that arises from the photonic spin-orbit interaction and subsequently show nonlocal correlations between two photons that interacted with the metasurface. Our results show that metamaterials are suitable for the generation and manipulation of entangled photon states, introducing the area of quantum optics metamaterials.

Disorder-induced optical transition from spin Hall to random Rashba effect.

Disordered structures give rise to intriguing phenomena owing to the complex nature of their interaction with light. We report on photonic spin-symmetry breaking and unexpected spin-optical transport phenomena arising from subwavelength-scale disordered geometric phase structure. Weak disorder induces a photonic spin Hall effect, observed via quantum weak measurements, whereas strong disorder leads to spin-split modes in momentum space, a random optical Rashba effect. Study of the momentum space entropy reveals an optical transition upon reaching a critical point where the structure's anisotropy axis vanishes. Incorporation of singular topology into the disordered structure demonstrates repulsive vortex interaction depending on the disorder strength. The photonic disordered geometric phase can serve as a platform for the study of different phenomena emerging from complex media involving spin-orbit coupling.